Electrical resistance composition



EXAMINER CROSS REFERENCE 8 5 8 Aug. 11, 1931 r 73 Z '6 65 74 (f 47 z ,iP umesA iLmM L, I 1 81 1 4 ymrao I srA-Tas'. rATaNr OFFICE, 7

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zmarm-ormxammncnmnwxonmsamwonxmamnmsasmnonsrosmnvnan'rr T amazon. aasrsrarca conosrnon' Application as June 14, 1529. semi 311,044.

7 x This invention relates to an electrical rebloclrs are composed of a binder and a con-' sistant material formed from a composit1on duc t1ngmedium mixed together in finely diin blocks and shapes and with varying charvided form ,in the ro ortions desired. acteristics. This material may be made to Whenthebinderisset, eb ocks are moulded have a comparatively high resistance, or it under pressure and afterwards cured. may be vaned in its composition to have a Heat 1s not used in the process, except in the comparativelylow resistance so that it may curing as hereinafterspecified.

a be used as a substitute for resistance coils, or- I e is Y wand for carbon resistance units, forgeneral purcement finel I oun Cement has 'ven m poses in an electric circuit. satis actory re I s or t purpose. ari- This composition is usable as a resistance ous materials ma be used for the resistance unit in electric circuits of varying capacities We accor g to the characteristics v according to the content of the composit on Y esire 1n the final product. The iollowing I and to the cross-section used as a conductor. materials are recommended for this purpose: -1 As the material 'may be drilled, ground and Mineral-black, powdered gggphite and powu machined,'its-cross-section can easily be regudered ca u n rborun lated with considerable precision. Itmay M1nera also be mounted in separate units of varying I a e 1s oun to have a d'ecid ecrease 1n sizes for difierent capacities. v resistance with increase in tem rature.

This composition as produced in blocks 15 Graphite has a better conductivity, t an min- 7 ractically impervious to moisture, that IS; eral black and is preferred for low resistance 7 it will absorb only a low moisture content. bl ks; but it is somewhat more diflicult to '1 v a However, in practice it may be saturated to i with the binder.

thisextent withaconductin sal ,preferably Thefollowing proportions give a block silver nitrasf s y eepmg; 11 having the characteristics resistance, am e so u 1on, and, as this material is not strength and durability desired: I

g; stable under the action of light, it may be 50 grams Portln 6- u 10 grams minstabilized by sub'ecting the blocks, after l b1 2 w a 5 9 the es of hydroge 13 3 e o powders aremixed first and the hi 0 2S), changin he lmpr lqn t water is then incorporated with it. The wet so ver sul hide ,si. Under-t e m1cr0 powder is compressed into the mould at the o scope if is found that this 1m regnation satressure ranging between 2,500 and 25,000

urates the Whole content an in r se the His. per square inch. The amount of water conductivity uniformly, which is desirable e d d a vary lightly with the pressure .35 r h p p intend used. -The mixture is known as the dry as- The construction and apphc tlon f 131115 rocess .'i. e.,"it does not flow as a liquid and in n o 'w be more f y understood 15110111 is therefore easy to handle in the mould.

' consideration of the f llow ng specification U After removing from the mould the blocks 1 and the accompanying drawings, selected to g a o d b; su Wig H l:

4 illustrate a form of the invention app ed to pre crab y is done y the ap- 0o resistance units, and wh p ca 1011 of a et of steam for about five Figs. 1, 2 an 3 illustrate P orm that hours which penetrates the blocks and insures thi mvention ma, take applied m use. -a thorough setting of the cement. Without Figs. 4 and .5. ow this mvention-applied this seasoning the blocks "are inclined to to a form of adjustable non-inductive resiscrumble,'are more fragile and their mechanio5 tance and 4 f cal resistance is'lowered. However the addi-- P Fig.6isa form of fixed resistance with electi n of as to the mix reduces the {tried connections at intervals. brittleness. The b ocks are placed in a wire w"dh is a carbonaceo This invention .18 concerned mainly with basket andenclosed'inthesteam chamber themanuiactureoftheresistanceblock. The during theseasonmg process. The blocks 10o cRoss REFERENCE may be air dried for a few days after the seasoning process or they may be further cured under water for a tune and used after g out.

. glocks of this composition have been subwater cured blocks were subject to a jet of steam as described and then immersed in water for a few days. It has been found that in the latter treatment the water immersion makes very little impression on the block, in fact, the extent to which the blocks absorb moisture is governed by the pressure used on the mould. The composition is close in the grain and under high pressure the moisture absorbtion is very low.

The characteristics of this composition will be understood from the following tests:

Composition Treatment in ohms (a) 83.3% Portland cement, Air dried 12,000

16.7% are] (1)) Same as Mo1st dried, water cured 00, (c) Same as a) Steam dried, water cured. 100,000 (d) 83.3% Portland cement, Air dried 2,000

10.7%1am black (e) Same as Moist dried water cured" 5,000

f) Sameas(d Steam dried,wateroured. 8,

) 83.3% Portland cement, Air dried Infinity.

16.77 wood charcoal. (11) Same Moist dried, water cured" 150, 000 (i) Sameasfl; Bteamdried,weiercmed.. 20,000,000 (3) wii7 gortla d eement, Air dried (1: Same is Moist dried, watereured 21o, 1) Same as (j Steamdried,watermred-- 150,.

m) 71.4% Portland cement, Air drled.. 11, 000,000

28.67 borundnm. (:1) Same 8 s lmfi.-- Moist dried, waieteured 1 ggl:

I (0) Same as (m)- Steam dried, water cured to g,%

I (p) 83. 3% Portland cement, Air dried 8, 000,000

16. 7% carborundum. 2 Same as Moist dried, water cured.- 150,000 r 95% Portland cement, Moist dried, water cured-. 6,000,000

6% lam blifck. (a) Same as (r? Steam dried, water eured-- 9, 000, 000

In general, it will be noted from the above tests that the electrical resistance of the material depends upon the composition, and

' upon the process of manufacture. The lower the content of the conducting material the higher the resistance; also, air dried blocks are usually lower in resistance than moist dried or steam dried; and moist dried and water cured blocks are usually lower in reeistance than steam dried, water cured blocks.

Thus the electrical characteristics of the material can be varied either in the mix, or in the process of treating after the blocks are moulded' This enables resistance blocks to be made for a great variety of purposes and in a variety of shapes.

Some of the common shapes of these blocks, for eneral use, are illustrated at 15, 16 and 17, igs. l, 2 and 3.

A common form of non-inductive resistance is shown in Figs. 4 and 5 in which the present compound, preferably using lamplack or graphite as the conducting element is used in the ring shaped band 19 mounted on the insulated base 18 and connectin with the terminal 22. The knob 23 is centra ly mounted in this ring and carries the contact arm 24 in engagement with 19, also the contact arm 25 in engagement w th the metallic ring 20 which connects to terminal 21. The arms 24 and 25 are electrically connected through the stem of the .knob 23. It is apparent that the resistance of the circuit between terminals 21 and 22 is varied by the movement of knob 23 to va the portion of the resistance 19 that is inc uded in the circuit.

A form of non-adjustable but variable resistance is shown in Fig. 6 in which the central bolt 74, through the insulated bushings 75 and 76 holds the parts together in cylindrical form. These parts comprise tubular sections 69, 70, 71 and 72 of various lengths of resistant material. These sections are mounted on the metallic collars 62, 63, 64, 65 and 66 and each of these collars are connected-with a terminal as indicated at 67 and 68. Conductors may be connected to 000 these terminals to include various lengths of resistant material in the circuit .as desired.

It will be understood that this product is 000 capable of being moulded and is capable of being machined so that it can be produced in almost any desired shape to very close limits. This, together with the fact that a which is applied to the composition in powder form. Other binders may be used for this purpose such as dental cement which has great mechanical strength, or gypsum which is comparatively soft and easily moulded.

Having thus described our invention, we claim: j

1. An electrical resistance material comprising a mixture of 50 grams Portland cement, 1O grams mineral black and 16 c. 0. water which has been moulded under pressure and seasoned by the application of additional moisture. a

2. An electrical resistant material comprising amixture of Portland cement with powdered mineral black and water which has been moulded under pressure to the shape desired.

EXAMINER 3. An electrical resistant material comnatures.

LINCOLN T. WORK. ELMER S. IMES. EDWARD A. EVERETT.

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